XXX1V INTRODUCTION. 
June 21. 1841. The balance magnetometer was adjusted with the aid of a 
horizontal needle and Karer’s compass, so that the magnet of the instrument 
should be at right angles to the magnetic meridian; the magnet was balanced and 
its sensibility adjusted by the small screws, and the fixed wires of the microscopes 
were made to be in the same horizontal plane. 
The crosses of gold wire were found loose, and it was necessary to substitute 
fibres of silk till July 2, when Mr J. Ante inserted silver wires. It was not 
found necessary to readjust the magnet, the bisection of the crosses being sufficiently 
horizontal. 
July 6. 1841. A difference of ten micrometer divisions was observed between 
the readings of the two micrometers, due to the line j oining the crosses not passing 
through the centre of motion. 
After July 26. 1841, the north pole of the magnet was towards the east ; 
before that date it was towards the west. 
40. Determination of the deviation of the line joining the bisection crosses 
from the magnetic axis. 
For this purpose the needle is reversed on its support ; half the difference of 
the readings in the two positions is the deviation. 
TABLE 14.—Observations to determine the deviation of the line joining the Bisection Crosses 
from the Magnetic Axis of the Balance Needle. 
July 27. 1841. July 27. 1841. Sept. 1. 1841. ote 2, 1841. Jan. 11. 1842. 
| 
-|| Mean of Mean of | Mean of | Mean of Mean of | Mean of || Mean of | Mea | || Mean of | Mean of 
Two Alter- Diff. || ‘two | Alter- iff. 'Two Alter- iff. || Two Alver- | Diff. Two Alter- 
Microm. |nate Two. i} Microm. |nate Two | Microm. |nate Two. |, Mierom. |} 12 wo. | Microm. |nate Two. 
| | Al | a | | 
—15:0 —120 
| 4+ 227°5 2 || —56:5 | — 13:7 8 || —286 
—12:3 34 2 9 || — 72 
—71'8 | —23-2 "6 || —242 
— 34-2 | — 96 
5 | : 58 || aio 
Ube 7 || eaves 
—195'1 |4 70:5 
+1186 31] 306-7 | +370-7|+ 60-2 
—1811 *9| 282-0] + 49-9 | + 356-8 
|+ 88:1|—235-1] 318-4 |/+343-:0|+ 46:8 
|—289:0|+ 27-7] 316-7 le (438 | +3210 
|— 27-8 2989] + 255 
| 73 | 
t+ tee ttt 
July 27.1841. Ist Series, Mean deviation, 153-0 ) Correction for deviation, N. pole 
BN ees ZO SeLIeSn 5, ion ot ers | LEG: Cast, «psc. wo DD) 
Sept. 1. ... EE) ca Oey vey Se mish yy AIP Tf : x 
OR a ten: 9" Cae SRR LO ae 2st} ax, ee + a ee 
sl ft, URS el n~. 5 TR etroer oe « 2:0 co es |. oe 
The first series of observations, July 27. 1841, giving some reason to conclude 
that the magnet, on reversal, found different bearing points, the supports of the in- 
strument were examined ; the marble base was found quite level, but the south agate 
Diff. 
